Low-carbon operation strategy for a 1000 mw unit under deep peak shaving: synergistic efficiency enhancement through multi-stage turbines and multi-unit flue gas waste heat recovery

Abstract This study proposes an integrated flue gas waste heat recovery and power plant consumption reduction (FGRER) system that aims to achieve low-carbon operation through two-stage efficiency. The system operates by (1) utilizing reheated steam to drive multi-stage small steam turbines that generate electricity for auxiliary plant operation, thereby reducing internal electricity consumption while reusing the exhaust steam for heat supply, and (2) utilizing flue gas waste heat to preheat feedwater, thereby reducing boiler fuel input. The energy efficiency of Scheme 2 is significantly improved compared to a conventional unit. Specifically, in the full-load operating range, the power supply coal consumption was reduced by an average of 6.5 g/kWh, the auxiliary power ratio was reduced by about 2%, and the heat consumption was reduced by an average of 166.08 kJ/kWh. This integrated approach effectively solves the energy efficiency bottleneck at low-load operation and provides a scalable pathway for decarbonizing large coal-fired units without compromising grid flexibility.